[Refactor] Separate Round logic into its own file (#570)

* Everything works, need to clean up

* cleanup

* fix rebase issue

* clang format

* docs

* clang format

* clang format

* address part of review

* Protect against edge case when discarding at end of hand

* Protect undiscard against popping a discarded card that doesn't exist

* Protect against out of bounds access to the `played` cards stack

* fix condition in `select_four_of_a_kind_cards_in_played_hand`

* change `get_played_top() + 1` to `get_played_size()`

* move `can_play/discard_hand` functions to round.c

---------

Co-authored-by: MathisMartin31 <mathis.martin31@gmail.com>

source/game/common_ui.c

@@ -4,6 +4,7 @@
 #include "game.h"
 #include "game/main_menu.h"
 #include "game/options_menu.h"
+#include "game/round.h"
 #include "game/round_end.h"
 #include "game/run_setup.h"
 #include "game/shop.h"
@@ -15,8 +16,8 @@ static enum BackgroundId background = BG_NONE;
 // Map to fill in for refactor
 static const BackgroundRenderCallback bgCallbacks[] = {
     [BG_NONE] = NULL,
-    [BG_CARD_SELECTING] = NULL,
-    [BG_CARD_PLAYING] = NULL,
+    [BG_CARD_SELECTING] = game_round_change_background_selecting,
+    [BG_CARD_PLAYING] = game_round_change_background_playing,
     [BG_ROUND_END] = game_round_end_change_background,
     [BG_SHOP] = game_shop_change_background,
     [BG_BLIND_SELECT] = game_blind_select_change_background,
@@ -25,19 +26,20 @@ static const BackgroundRenderCallback bgCallbacks[] = {
     [BG_MAIN_MENU] = game_main_menu_change_background,
 };
 
+enum BackgroundId get_current_background(void)
+{
+    return background;
+}
+
 void change_background(enum BackgroundId id, bool force_redraw)
 {
     if (force_redraw)
     {
         background = BG_NONE;
-        reset_background();
     }
     if (id != background && bgCallbacks[id] != NULL)
     {
         bgCallbacks[id]();
     }
     background = id;
-
-    // Can be removed once all states have their own "change_background" func
-    change_background_legacy(id);
 }